Question

简便计算99.9＋999×9.9

Answer 1

99.9＋999×9.9
=999×0.1＋999×9.9
=999×（0.1+9.9）
=999×10
=9990

Answer 2

=99.9+99.9×99=99.9×﹙1+99﹚=99.9×100=9990

Answer 3

999*0.1+999*9.9
=999*（0.1+9.9）
=9990

Answer 4

=99.9*1+99.9*10*9.9
=(1+99)*99.9
=9990